 Pythagorean Theorem  Over 20 Proofs  Interactive Mathematics Miscellany and Puzzles, Alexander Bogomolny
A general exposition of the Pythagorean theorem, with proofs from Euclid to Garfield  and more. Also links to other sites on the Web with proofs.
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 Pythagorean Triples  H.B. Meyer
A Javascript calculator for pythagorean triples. In English and German.
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 Pythagoreisches Tripelprogramm  Heinz Becker
A Java applet that reads a and gives integer solutions of a^2+b^2 = c^2. In German and English.
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 Pythagoräische Tripel (Pythagorean Triplets)  H. B. Meyer
A calculator for Pythagorean triplets, making visible the oneto one correspondence between triplets and certain pairs of relatively prime numbers, and an interesting correspondence with certain sequences of letters A, B, or C. (Javascript is required.)
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 Pythia Equation Solver  Pablo Perna
The site contains equations for which the user can solve automatically any unknown given the known parameters. Geometry equations include areas of triangles and circles, and surface area and volume for various 3D shapes. Equations also include electronics
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 Qdos Math  The Education Channel International, Ltd.
An interactive online program delivering elementary mathematics content. Written by teachers, the program includes assessment tests, interactive tuition/demonstration pages and followup exercises and activities. Qdos is available via the internet at
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 QPuzzle  XIAO Gang
A mathematical jigsaw puzzle: your goal is to recover a disordered photo by finding the inverse affine transformation. A French version is also available.
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 Quadramania  CleverMedia
Use tiles of different shapes to form rectangles and earn points  ten times the square of the total number of tiles in the rectangle. Requires the Flash plugin.
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 Quadratic Map  Ron Lee
The Quadratic Map is the chaotic dynamical system composed of the following equation: x_n+1 = 4 lambda x_n(1  x_n) with parameter lambda. The Java applet is a quadratic distribution plotter.
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 QuantumBrainBenders  Joel Klebanoff
A series of puzzles: find a series of numbers in a grid that add to the given sum. A new puzzle for each of three skill levels is posted daily. The site also includes an archive of previous puzzles.
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 QUdata.com  Icestone Trustee Limited
Online tools and reference library resources for data mining and knowledge discovery. Collection of free online statistical and scientific calculators, 2D and 3D function plotters.
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 Queryous  Information Manipulation, Inc.
An interactive quiz tool. Take a quiz on any course currently available or create your own course and earn half the proceeds. Businesses may use this for training or create free courses for brand recognition.
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 QueryTree  D4 Software Ltd
Drag and drop this free tool to explore, analyze, and visualize data — without special code, formulas, or even software: QueryTree queries tabular information within your web browser.
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 The Quest for the Holy Value  Kjetil Valstadsve
Finding the correct value of pi. The likelihood of any random two integers having 1 as their greatest common divisor (no factors in common), has been proved to be 6 divided by pi squared  the numbers are prime in relation to each other. According to
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 Quia!  The Learning Group
Create your own Javaenabled quizzes, home pages, and learning games to play over the Internet: enter your material into a form, select a few options, and press a button. Games have been created and are available for browsing in mathematics, as well as:
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 Quite BASIC  Nikko Strom
A JavaScript environment for coding in the classic BASIC programming language. Math projects include the Fibonacci Sequence, Fibonacci Squares, the Sieve of Eratosthenes, and Mandelbrot; puzzles include the Towers of Hanoi and variations of the Eight
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 Quiximity  CleverMedia
Race against the clock to find threeofakind that match in color or shape, earning point bonuses for objects adjacent to one another. Requires the Flash plugin.
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 Quizma > Matemática Cálculo Robótica  Harold Suárez Guzmán
In Spanish: Clases y Orientación en Matemáticas Cálculo y Robótica. Fórmulas  Demostraciones  Ejercicios  Ejemplos  Cálculo Interactivo. Algebra, Logaritmos, Trigonometría, Geometría, Estadística, Ecuaciones, Problemas de Planteo, Funciones, Geometría
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 Quiz Me  D. Kell and Mercer County Community College
Interactive quizzes constructed using software provided by Addison Wesley Longman Publishers. Autoscoring, multiple choice selftests on whole numbers (place value, operations, applications, rounding, roots and order of operations); fractions (equivalencies,
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 QuizTree Math Games  Sierra Vista Software
A collection of online math quizzes in addition, subtraction, multiplication, and division.
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 Quizzes.cc
Use the menus and text boxes to create your own quizzes on addition, subtraction, multiplication, and division  or browse from among a selection. Click the appropriate button to reveal answers, grade responses, or generate new problems.
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 Radius and Diameter  NASA Lewis Learning Technologies Project
Mr. Jordan wants to put up a fence all the way across the middle of his round vegetable garden. If the radius of the garden is 3 feet, how many feet of fencing will Mr. Jordan need to buy? A detailed answer is provided. From NASA's 9th Grade Math Proficiency
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 Rainforest Maths  Jenny Eather
Flashbased interactive mathematics activities with an Australian rainforest theme, for grades K through 6. Topics include: Number & Number Systems; Operations & Calculations; Strategies & Processes; Patterns & Algebra; Measurement; Space & Geometry;
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 random.org  Mads Haahr
Generate random numbers on the Internet by using a web form (comparable to throwing dice), randomized sequences (lottery tickets), raw random bytes, virtual coin flips, or bitmaps. All numbers are tested statistically and the results available in realtime.
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 Random Walk Along a Line: A Simulation  David Sumner; University of South Carolina
A Javascript simulation of a particle moving along a straight line with absorbing states at either end. Modifiable variables: length of the line, starting position of the particle, number of trials. The theoretical expected length of a walk with these
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 RapidCalculator  ProAlgorithms.com
This mobile computing platform for web and handheld devices performs matrix operations like multiplication/inverses; plots graphs of functions and operations on polynomials; manipulates complex numbers; and evaluates other math, science, and engineering
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 Ratio and Proportion  NASA Lewis Learning Technologies Project
If the ratio of boys to girls is 5 to 8 and there are 40 girls, which proportion should you use to find out the number of boys? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Rational Number Tutorial  Joseph L. Zachary
A tutorial that explores the nature of rational numbers, the significance of the minimum and maximum integers in a rational number system, and the meaning of overflow. Includes a Java applet that opens in a separate window, for use alongside the tutorial.
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 Raw  DensityDesign Lab
The "missing link between spreadsheets and vector graphics," this open web app's interface lets you create custom vectorbased visualizations on top of the DataDriven Documents JavaScript (D3.js) library. Starting with delimiterseparated values in plaintext
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 Reasoning Mind  Reasoning Mind Inc.
Reasoning Mind is a nonprofit organization. It's also a core curriculum based on programs proven successful in Russia, China, and Singapore. A Reasoning Mind classroom combines a teacher and the computer, aiming to get kids so interested in math they'll
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 Rectangle Perimeter and Side Length  NASA Lewis Learning Technologies Project
A rectangle with a perimeter of 24 inches might have adjacent sides measuring: 6 inches and 4 inches; 11 inches and 13 inches; 9 inches and 3 inches; or, 2 inches and 12 inches? A detailed answer is provided. From NASA's 9th Grade Math Proficiency Test.
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 Recursos de Matemáticas para 2º de Bachillerato y 1º de Carrera de Ciencias  Matemáticas de Bachiller
In Spanish: Libros que puedes hojear; videos que puedes ver introducción al Álgebra de lo Lineal, introducción al Cálculo Diferencial, introducción al Cálculo Integral, ejercicios de examen de Selectividad, Know How; Detector de Pardillos Matemáticos;
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 Regression Applet  R. Webster West, Dept. of Statistics, Univ. of South Carolina
An applet designed to teach students the effect of leverage points on a regression line. Students may add points to the plot by clicking the mouse button. By adding points far from the existing line, the regression line changes considerably. This is particularly
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 Regression Tools
Online, Flashbased regression tools for linear, logarithmic, exponential, power, polynomial, multiple linear, multiple polynomial, and nonlinear regression.
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 Relative Prime Applet (MSTE)  Nicholas Exner; University of Illinois at UrbanaChampaign (UIUC)
A Java applet that compairs pairs of numbers to see whether they are relatively prime. The main goal of this action is to demonstrate the theorem that the probability of two positive integers chosen at random being relatively prime is six divided by pi
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 Remote Interactive Optimization Testbed (RIOT)  Industrial Engineering and Operations Research, UC Berkeley
Interactive educational and research tools for optimization problems. Applications: Learn about practical applications of optimization technology to Major League baseball, openpit mining, computer network design, and modular parts fixturing. Experiment
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 Repeated Prisoner's Dilemma Applet  Mike Shor
A repeated prisoner's dilemma game in which the user plays for twentyfive
rounds against each of five different (unknown) 'personality types'. Demonstrates the value of cooperation and the ability to take advantage of
some simple rules.
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 Research Institute of Symbolic Computation (RISCLinz)
The Research Institute for Symbolic Computation, RISC, is an Austrian institute devoted to the field of symbolic computation. The site includes descriptions of various research areas, such as combinatorics, constraint solving, the theory of computation,
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 Research  Peter Alfeld; University of Utah
Researchrelated materials: An interactive applet that lets you explore the BernsteinBézier form of a bivariate polynomial; recent papers, complete bibliography, recent talks, computer graphics (illustrating various mathematical concepts: US Global Positioning
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 The RetroPsychoKinesis Project  Peter Moore and John Walker
Retropsychokinesis (RPK) is the claimed ability of certain subjects to alter random data generated, but not examined, prior to the time the data are presented to the subject. Read about or run bell curve, clock face, or pendulum feedback programs (Java
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 Rice Virtual Lab in Statistics  David M. Lane, Rice University
A comprehensive interactive resource for studying statistics, in four modules: HyperStat Onlinean introductorylevel hypertext statistics book, with links to other statistics resources on the Web; simulations/demonstrationsJava applets that display
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 RICHplot  Richard Davies
A Java applet for plotting userdefined trigonometric functions. Includes the following functions: sin, cos, tan, abs, sqrt ,+ , ,* ,/ ,^ (power function), asin, acos, atan, ln (log to the base e) and exp. Requires a Javaenabled browser.
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 The RightAngle Triangle Solver  Steve Ayers
Input two sides of a right triangle, or one of its sides and one of its angles, and this site calculates the remaining sidelengths and angles. Also, convert decimals and fractions, and imperial and metric units of measure. Requires JavaScript.
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 Rincón Matemático Tests interactivos  Mario A. Bunge
Exámenes multiple choice de Precálculo, Matemática, Análisis Matemático y
Álgebra lineal. Cada examen se presenta en dos formatos: PDF y HTML.
El PDF se imprime y se utiliza como una hoja de examen. Realizada la
prueba, se recurre al HTML (quiz
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 RngPack  Paul Houle
A pseudorandom number generator package for Java. Pseudorandom means that the "random" numbers are generated by a deterministic mathematical process, not by a fundamentally random physical process such as radioactive decay or Johnson noise. RngPack contains
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 Robert Abbott's Mazes  Robert Abbott
Two very difficult puzzles programmed by Oriel Maxime and based on mazes in Abbott's books: the Sliding Door Maze, and Theseus and the Minotaur. Also a collection of reviews of the books SuperMazes and Mad Mazes, with more puzzles (but nothing interactive),
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 Robert's Online Applications  Robert Lum
Java applets to assist with financial investments: commissions pricer, derivatives pricer, loan pricer, option pricer, option strategy visualizer, portfolio pricer, quote sheet, stock volatility charts, and tax pricer (1999, 1998, 1997, 1996 or 1995).
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 Robo Compass
"Geometrical constructions made easy": type commands such as "draw segment AB between points A and B" and "construct an arc z with center O and radius which is length of segment y," then watch Robocompass draw the construction onscreen with its animated
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 Rolf's Calculator  Rolf Howarth
A fully featured JavaScript scientific calculator that includes trig functions and logarithms, factorials, 12 levels of parentheses, logs to base 2, bitwise logical operators, hex, octal, binary and ascii display.
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 Roman Numeral Date Conversion Guide  Christopher Handy
A guide to deciphering Roman numeral year dates as commonly found in both modern and early printed books, including a Java applet that accepts Roman numeral input in the range 14,999 and converts it to Arabic form. The page explains the basic principles
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